The proposed research is concerned with the development and application of statistical mechanical theories for assemblies of amphiphilic molecules in solution. The fundamental analysis of the competition between hydrophobic and hydrophilic effect in these systems seems central to understanding biochemical phenomena. Two general classes of systems will be considered: micelles and proteins. For the former, the objective is to begin with relatively realistic intermolecular potential models and to arrive at reasonably simple theoretical predictions of thermodynamic and structural properties of aqueous surfactant assemblies. For the latter, the objective is to derive a systematic and practical microscopic basis for the virtual bond formulation and related simplications of protein modeling. Recent advances in liquid state theory have now made these realistic goals. New extensions of the RISM integral equation theories provide practical and accurate methods for determining solvent induced interactions between the elementary groups composing surfactant molecules or polypeptide chains. With these interactions in hand, the remaining statistical mechanical calculations involved with the assembly or conformation of amphiphiles can be performed with the aid of recently developed field theory methods including generalizations of Feynman's polaron theory and also the renormalization group method.